Backplanes are printed circuit boards or metal plates on the upper sides of which daughter boards are detachably mounted perpendicular to the backplanes for easy removal. One way of electrically connecting a daughter board to another daughter board, the backplane, and other circuitry is by a two-piece multiple contact connector consisting of a backplane connector element that is attached to the backplane and a mating daughter board connector element that is attached to the daughter board and fits between upwardly extending sidewalls of the backplane connector element. When the two elements are joined, the plurality of rows of post contacts directed upwardly between the sidewalls of the backplane connector element are connected to a plurality of corresponding downwardly directed forked contacts of the daughter board connector element.
In High Density Plus backplane-daughter board connectors manufactured by Teradyne Connection Systems, Inc., additional flat ground contacts are carried by the wall of the daughter board connector element and are contacted by discrete upwardly directed contact portions of ground contacts carried by the facing wall of the backplane connector element. Projections of the flat ground contacts and the ends of the forked contacts are secured in rows of holes that pass through the daughter board.
Some daughter boards have internal ground plane layers precisely spaced from the signal lines on their surfaces in order to have controlled impedance (to reduce signal reflection caused by changes in impedance) and reduced inductance in the ground path during high-speed switching. The internal ground plane layers have been electrically connected to backplanes through plural mating pairs of forked contacts and post contacts, and also through the flat ground contacts of the High Density Plus connectors.